New Pentagon data show U.S. troops are killing themselves at the rate of nearly one a day so far in 2012, 18% above 2011’s corresponding toll. “The continual rise in the suicide rate has frustrated all in the military,” says Elspeth “Cam” Ritchie, a retired Army colonel and chief psychiatric adviser to the Army surgeon general. “The rise in the suicide rate continues despite numerous recommendations from the Army and [Department of Defense] task forces.”

There were 154 U.S. military suicides in the first 155 days of 2012, the Associated Press reports, compared with 130 over the same period last year. That’s 50% more troops than were killed in action in Afghanistan, and the highest suicide toll in the U.S. military since 9/11.

Suicide — and the reasons for it — has been a vexing problem for the U.S. military ever since its rate began eclipsing that of the U.S. population. In 2010, the Army noted that “historically, the suicide rate has been significantly lower in the military than among the U.S. civilian population.”

But that began to change as the wars in Afghanistan and Iraq — initially thought of as short-term affairs — dragged on for years. More critical than their duration was the fact that a relatively small number of U.S. troops kept being sent back for multiple combat tours.

Repeated tours have driven up the rate of posttraumatic stress disorder, which in turn generates an increase in suicide attempts among those suffering from PTSD. Even though many troops who have killed themselves did not deploy, they trained amid the dread of those who did. There is a sense, some service members say, that suicide — or at least suicide attempts — can be contagious.

“There are two areas which we should explore further,” says Ritchie, a regular Battleland contributor. “The high optempo [operations tempo] of deployed units, which means that leaders do not really know their soldiers; and the easy availability of firearms, the ‘gun in the nightstand,’ which, unfortunately, leads to too many impulsive suicides, and occasionally homicides.”

The Army’s suicide rate eclipsed the age-adjusted civilian rate in 2008, more than six years after the 9/11 attacks that sparked the wars in Afghanistan and Iraq. Suicide may follow in the wake of its triggers — it can take years for deployments, or the prospect of deployments, to sink in and lead some service personnel to take their own lives. Suicides will likely continue to rise for a while, even as the U.S. military has ended its war in Iraq and winds down its presence in Afghanistan. “It can be called a lagging indicator,” Ritchie says.

That may not make a lot of sense, but no one ever said the act of taking one’s life is logical. If it were, the legions of military mental-health professionals focused on combating it would have figured out how to halt this epidemic by now.